Method for producing acrylonitrile polymer fibers and filaments by wet spinning process



United States Patent 3,080,209 METHOD FOR PRODUCING ACRYLONITRILEPOLYMER FIBERS AND FILAMENTS BY WET SPINNING PROCESS Yoshisato Fujisaki,Numazu-shi, and Toshio Ohfuka,

Fnji-shi, Japan, assignors t0 Asahi Kasei Kogyo Kabushiki Kaisha, Osaka,Japan, a corporation of Japan Filed Oct. 12, 1961, Ser. No. 144,533 6Claims. (Cl. 18-54) This invention relates to the preparation of fibersand filaments from acrylonitrile polymers by extruding a solutionthereof in nitric acid into an aqueous nitric acid medium and drying thecoagulated fibers or filaments. More particularly, this inventionrelates to a production of acrylonitrile fibers and filaments havingsuperior dyeability for basic dyestufis by incorporating univalentcations consisting of ammonium or alkali metal ions in the fibers andfilaments.

In a well known method for preparing fibers and filaments ofacrylonitrile polymers acrylonitrile polymer is dissolved in nitric acidat a temperature of below G, extruded into dilute nitric acid at a lowertemperature and stretched at a high temperature. Although it may bepossible to produce fibers and filaments having excellent qualityaccording to such method using nitric acid as a solvent, in many casesfibers and filaments having homogeneous and high afiinity for the basicdyestuffs are hardly obtainable depending upon the properties of theinitial polymer.

It is, therefore, an object of the present invention to provide a methodfor improving dyeability of acrylonitrile fibers and filaments for thebasic dyestuffs.

It is an another object to provide acrylonitrile fibers and filamentshaving superior dyeability for basic dyestufis.

In the present specification, acrylonitrile polymers includepolyacrylonitrile and polymers or copolymers containing at least 85% byweight of acrylonitrile and not more than 15% by weight ofmonoethylenically unsaturated compounds copolymerizable therewith. Themonoethylenically unsaturated compounds comprise, for instance, esterssuch as methyl acrylate, ethyl methacrylate, vinyl acetate and the like;amides such as acrylamide, methacrylamide and the like; alcohols such asallylalcohol and the like; ketones such as methyl vinyl ketone and thelike; acids such as acrylic acid, methacrylic acid, itaconi;

acid and the like; sulfonic'acids such as para-styrene sulfonic acid,vinyl sulfonic acid, sulfoethyl acrylate, sulfopropyl methacrylate andthelike; vinyl chloride'andvinylidene chloride, but basic comonomerssuch as vinyl-pyridine and the like are not included.

Any basic dyestuffs may be used in the present process. Typical examplesare Sevron Yellow L, Sevron Yellow R, Sevron Orange L, Sevron BrilliantRed 4G, Sevron Red L, Sevron Red GL, Sevron Blue B, Sevron Blue 2G,Sevron Blue 5G, Sevron Green B, Du Pont Fuchsine Conc., Du PontBrilliant Green Crystals, "Du Pont Victoria Green Small Crystals,Basacryl Yellow 3GLH, Basacryl Red 6BH, Basacryl Yellow SGL, BasacrylBlue GL, Basacryl Violet RL, Astrazon Blue FGL, Astrazon Orange R,Astrazon Yellow 7GL, Astrazon Blue 3RN, Astrazion Red BBL, Astrazon Red6B, Astrazon Pink FG, Astrazon Yellow 3G, Maxilon 3GL, Maxilon Blue GL,Maxilon Red BL, Genacryl Yellow 5GP, Genacryl Yellow 36, Genacryl Red63, GenacrylBlue 6G, Deorline Yellow SGL, Deorline Red 53, Deorline Blue5G, Cathilon Yellow SGLH, Cathilon Orange GLH, Cathilon Blue BLH,Bismark Brown and Magenta.

Acrylonitrile polymer is first dissolved at lower temperature in nitricacid solvent (63% by Weight or higher), extruded into a 25 to 45 weightpercent nitric acid coagulation bath, washed with water, stretched to 4to 20 times in hot water, superheated (unsaturated) steam, superat- "icemospheric (saturated) steam or atmospheric pressure C.) steam or hotair, and is then dried in the conventional way.

According to the present invention, the fiber after leaving thecoagulation bath is treated with a solution containing univalent cationsbefore drying in order to incorporate the cations in the fiber. Cationscontained in the polymer or in the spinning solution are removed in thecoagulation bath from the fibers, so that they are no longer active.Even when a large amount of cations is added to the coagulation bath toincorporate it into the fibers, the cations are still washed off in thefinal washing with water and are not active. The univalent cations arelithium, sodium, potassium and ammonium. They are used in the form of anaqueous solution of water soluble inorganic salts of such acids asnitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boricacid and the like. Salts with organic substances such as sodium laurylsulfate are not desirable, since after being dyed with the basicdyestuff there occur defects in either fastness to washing or to light.

It is preferable to immerse the coagulated fibers and filaments in abath of said aqueous solution of water soluble inorganic salts, at anystage after leaving the coagulating bath and before entering a dryingstep. In some cases, before drying, the coagulated fibers and filamentsmay be dehydrated by passing between rollers. However it is essentialthat the fibers and filaments must not have undergone drying before theimmersion to an extent that the water content is less than 15% by Weightbased on the swelled gel and, preferably, the water content should notbe less than 45%. The aqueous solution of inorganic salts may be pouredor sprayed onto the filament or fiber.

Incorporation of the univalent cations in the fiber helps to prevent theloss of groups active to basic dyes from the acrylonitrile polymer andto improve the penetration velocity or diffusion velocity of the dyesinto the fiber, thus to improving dyeability of the fibers.

Univalent cation is incorporated in the fibers preferably in aconcentration range about from 0.003 to 0.02 mol/ 100 g. fibers, basedon the dry weight of fibers. Dyeability of the fibers increases to acertain extent in proportion to the increase in the concentration of theunivalent cations in the fibers. However, above the stated limitation,the increase in dyeability becomes very slow and also various defectsare caused to arise, such as the decrease in whiteness or the loss oftransparency of the fibers.

The polymers used in the present invention can be produced by any of thegeneral methods which are well known and there is no particularlimitation.

The accompanying drawings, FIGS. 1-3, show outlines of methods forimpregnating coagulated filaments with salt in accordance with thepresent invention.

A spinning solution after cooling is filtered, introduced to a spinneret2 through a conduit 1, and extruded at a fixed rate into a coagulatingbath 3 to produce a coagulated filament 4.

As the coagulating bath, 25-40% (weight) nitric acid is ordinarilyemployed. The coagulated filament is introduced into a water washingbath 6 through rollers 5 wherein the acid content thereof is removedupon passing of the filament over rollers 7 and 8 before the filament issubjected to the salt-impregnating operation of the present invention.For example, the most convenient process is to apply the treatment ofthe present invention after the' coagulated filament has beenhot-stretched. This is shown in FIG. 1, wherein a salt-impregnating bath12 is provided next to a hot-stretching bath 9 (10, 11, 13 and 14 areguide rollers). Generally the coagulated filament is stretched to 4 to20 times in the hot-stretching bath which may be placed at any desiredposition throughout the process. As to the hot-stretching bath, hotwater is ordinarily used, but the water may be substituted byunsaturated superheated steam or saturated atmospheric orsuperatmospheric pressure steam. In spite of a hotstretch-ing operation,the coragulated filament does not suffer from such reduction of itsdegree of swelling which would prevent the salt-impregnating operationof the instant method.

In case the unsaturated superheated steam or saturated atmospheric orsuperatmospheric pressure steam is employed as the hot-stretching bathin place of hot water, it is possible to place the salt-impregnatingbath before the stretching process, since the coagulated filament is notde salted during the stretching operation. One example thereof is shownin FIG. 3, wherein 17 is the salt-impregnating bath, is is a tubularhot-stretching tube and 18, 19 and are guide rollers.

These steps can suitably be modified within the general concept of thepresent invention. For example, in case the hot-stretching bath isconducted in hot water, the stretching bath may be used as asalt-impregnating bath. FIG. 2 shows one example thereof wherein awaterwashed coagulated filament is hot-stretched in a saltcontaininghot-stretching bath 16.

Furthermore, even though hot water is employed as the stretching bath,if a small amount of salt is employed in the bath it is possible tocontrol the amount to be desalted, and the salt-impregnating bath may beprovided before the stretching process. Also, in case a relatively largeamount of salt has previously been added to the salt-impregnating bath,it is readily possible to hot-stretch the coagulated filament in hotwater after treating it in the salt impregnating bath. Further, anadditional saltimpregnating bath may be placed after said hot-stretchingbath to control the salt content of coagulated filament. However, incase hot dried air is used as a heating medium of the stretching bath,the lowering in swelling degree during stretching is relatively large sothat it is preferable to provide the salt-impregnating bath before theheatstretching process. Although it is of course possible in theory tocarry out a process for incorporating salt in the coagulated filament bywashing said filament with water containing salt in the Water bath, suchprocess is not desirable from the economical point of View.

The method of the present application is not restricted to the processjust described. For instance, the waterwashing and hot-stretching stepsare not limited to merely one stage but can be carried out in amulti-stage process. Also, when a multi-stage stretching is conducted,there are some cases where a drying step is inserted among said stages.Moreover, in case the hot-stretching is carried out by a multi-stageprocess, there is oftentimes adopted such a condition that thetemperature of each stage is elevated successively. Further in theaforesaid drawings, the squeezing rollers may be replaced by Nelson typerollers or multi-stage rollers. As mentioned above, all the well knownprocesses may ordinarily be employed in connection with the instantmethod. All the variations would not depart from the basic idea of thepresent invention as set out in the appended claims. i

The following examples illustrate the present invention without limitingits scope. i

EXAMPLE 1 145 parts of a copolymer consisting of 92% of acrylonitrileand 8% of methyl acrylate (ploymerized by using the initiator system ofK S O and thioglycollic acid; molecular Weight: 50,000) were dissolvedin'85.5 parts of 72% HNO at 3 C. This solution was extruded into acoagulating bath of 33% 'HNO maintained at 3" C. through a spinnerethaving 2,000 holes'of 0.1 mm. diameter each. After being thoroughlywashed with water, the filament was stretched to 10 times its length ina boiling water bath maintained at a pH of 3.5 by sulfuric acid. Theamount of NH in a stretching bath was varied using NH while maintainingthe pH constant.

The stretched fibers thus obtained were dried at C. in air for 30minutes. In order to examine the dyeability of these fibers with thebasic dyestuffs, they were dyed in a 0.0625 solution of malachite greenhaving a pH of 3.5 with fiber to liquor ratio of 1:40, at C. for onehour. The dyeability of the fiber thus obtained is shown in Table l. Thedyeability is defined as the percent ratio of the amount of dyestutfsabsorbed in the fiber to that of dyestutfs originally present in thedyeing bath.

Concentration of N Hr in fibers (incl/100 Dyeability Whiteness of g.fiber) (percent) fibers 13 bright. 15 Do. 18 Do. 24 D0. 33 D0. 40 Do. 53slightly bright. G8 slightly dark. 69 Do. 70 dark.

When these dry fibers were steamed at C. for 10 minutes, the dyeabilitybecame as follows:

Fibers not containing NH ion:ca. 0% Fibers containing 0.0067 mol/100 g.fibers of NH EXAMPLE 2 A copolymer consisting of 97% of acrylonitrileand 3% of sodium acrylate (polymerized by the initiator system of K S Oand NaHSO molecular weight: 47,000) Was dissolved in 65% nitric acid at5 C. This solution was extruded into 38% nitric acid containing 1% ofammonium nitrate at 0 C. After being washed thoroughly With Water, thiswas stretched in the stretching bath maintained at a pH of 3.5 bysulfuric acid and squeezed by means of rollers until the water contentthereof becomes 50%. This was immersed in a bath having variousconcentrations at Na HPO and then dried in air at 90 C. for 30 minutes.The dyability and the whiteness of the fibers dyed by the same processas described in Example 1 are set forth in Table 2A.

Table 2A Dyeability (percent) Whiteness of 30 slightly bright. 32 do.

98 slightly dark. 98 dark.

To the fibers, was added 40 times by weight of a 0.125% by weight SevronRed L solution (pH=5) and the mass EXAMPLE 3 A copolymer consisting of97.3% of acylonitrile, 2% of acrylamide and 0.7% of sodium salt of3-sulfopropyl methacrylate (polymerized by the initiator system ofsodium hydroxynitrilosulfonate and NaHSO molecular weight: 48,000) wasdissolved in 72% nitric acid containing 1% of magnesium nitrate,maintained at C. This solution was extruded into 30% nitric acidmaintained at 3 C. After washing thoroughly with water, the fiber wasstretched to 6 times its length in a stretching bath kept at a pH of 4by phosphoric acid and then was squeezed until the water content becomesabout 65% by means of rollers. Then the fibers were immersed in anaqueous potassium sulfate solution having various concentrations of K+ion and in aqueous potassium lauryl sulfate solution, respectively. Thefibers thus stretched were dried at 80 C. These fibers were dyed byplacing them in a dye solution containing 0.0875% of Sevron Red L, at apH of 5 (fiber to liquor ratio; 1/40'), and treating at 100 C. for 2hours. After thoroughly washing with water, the fibers were dried at 80C. The fibers were put in a 0.5% aqueous solution of Marcel soap of 50times the weight of the fibers. Then a cotton cloth was immersed thereinand the solution was treated at 70 C. for minutes. The extent ofcontamination is shown in Table 3.

Table 3 Extent of contamina- K+ ion concentration in fibers tion ofcotton cloth 0.017 0.012 (introduced in as potassium lauryl sulfate)-Do. much contaminated.

EXAMPLE 4 A copolymer consisting of 94% of acrylonitrile and 6% ofmethyl methacrylate (polymerized by the initiator system of potassiumpersulfate and fl-mercaptoethanol; molecular Weight: 43,000) wasdissolved in 70% nitric acid at 3 C. and was extruded into 34% nitricacid maintained at 3 C. After Washing thoroughly with water, thematerial was stretched to 6 times in a bath at 100 C. of pH 3 by meansof sulfuric acid and was dried in a dryer at 70 C. to vary the watercontent ratio (based on the Weight of swelled gel). Then, the fiberswere immersed in an aqueous potassium nitrate solution and were treatedto contain K+ ion in the fibers. After drying until the water contentbecame about 4%, the fibers were dyed according to the same method asdescribed in Example 1. The results are shown in Table 4.

EXAMPLE 5 A copolymer consisting of 93% of acrylonitrile and 7% of vinylacetate (polymerized by the initiator system of sodiumhydroxynitrilosulfonate and NaHSO molecular weight: 51,000) wasdissolved in 77% nitric acid at -5 C. and was extruded in 37% nitricacid maintained at 5 C. After being coagulated, the fiibers were washedwith water and stretched to 5 times in boiling Water. The fibers thenwere immersed in an aqueous solution containing about 0.01 mol/100 g. HO of various cations. Then, the material was dehydrated by means of acentrifugal separator until the water content ratio became about 50% andwas dried at 70 C. In this instance, cations were contained in an amountof about 0.01 mol per 100 g. of dry fibers. The results obtained bydyeing said fibers according to the same method as set forth in Example1 are shown in Table 5A.

Non-treated, NaCl-treated or MgCI -treated fibers mentioned in Table 5A,were dyed with solutions of various dyes (pH=3.8) at a fiber to liquorratio of 1/40, at 100 C. for 1 hour. The results are set forth in Table5B.

Table 5B Cone. Kinds of ion treated Kinds of dyes of dye.

percent none NaCl Mgtll Sevron Blue B 0.20 30 99 28 Sevron Green B 0.3023 77 20 Sevron Brilliant Red 4G 0.25 20 64 21 Basacryl Red GL 0.25 2067 18 As appears from the above table, bivalent and trivalent metals arenot effective in improving dyeability but rather bring about undesirableinfluences.

EXAMPLE 6 A copolymer consisting of 98.5% of acrylonitrile and 1.5% ofmethallyl sulfonate (polymerized by the initiator system ofazobisisobutylonitrile and lauryl mercaptan; molecular weight: 53,000)was dissolved in 70% nitric acid at 5 C. and was extruded into 33%nitric acid maintained at 5 C. The material was washed thoroughly withwater after being coagulated and was squeezed by means of rollers sothat the water content ratio became 80%. These squeezed fibers wereimmersed in an aqueous solution prepared by dissolving 0.7 g. of Na HPOper 100 g. of Water and maintained at a pH of 2.8 by sulfuric acid atroom temperature. Then, the fibers were stretched to 6 times in steamheated to 120 C. and were dried at 100 C. after squeezing until thewater content ratio became 50%. 0.009 mol of Na was contained per 100 g.of this fiber. The dyeability of this fiber obtained by dyeing accordingto the same method set forth in Example 1, was 32%. When similar fiberswere prepared according to the same method without employing any Na HPOthe dyeability was 8%.

What we claim is:

1. In a wet spinning method for producing fibers of acrylonitrilepolymers selected from the group consist- 111g of polyacrylonitrile andcopolymers of at least by weight of acrylonitrile and up to 15% byweight of monoethylenically unsaturated monomers copolymerizabletherewith the said method involving dissolving the polymers in a nitricacid solvent, extruding and spinning the solution thus obtained in acoagulating bath and drying the spun article, the improvementcomprisiing treating the fibers with a water soluble, univalentcationcontaining inorganic acid salt until the univalent cation isincorporated in the fiber to the extent of between 0.003 and 0.02 molper gram fibers, the said treatment being effected after carrying outthe coagulation and before reducing the water contents of the fibers inthe drying to below 15% and the said univalent cation being selectedfrom the group consisting of ammonium and alkali metal ions.

2. The method of claim 1 wherein the alkali metal ions are selected fromthe group consisting of sodium and potassium ions.

3. The method of claim 1 wherein the water soluble inorganic salts areselected from the group consisting of salts of sulfuric acid, phosphoricacid and nitric acid.

4. In a wet spinning method for producing fibers of acrylonitrilepolymers selected from the group consisting of polyacrylonitrile andcopolymers of at least 85% by Weight of acrylonitrile and up to 15% byweight of monoethylenically unsaturated monomers copolyrnerizabletherewith the said method involving dissolving the polymers in a nitricacid solvent, extruding and spinning the solution thus obtained in acoagulating bath and drying the spun article, the improvement comprisingtreating the fibers with a water soluble, univalent cationcontaininginorganic acid salt until the univalent cation is'incorporated in thefiber to the extent of between 0.003

and 0.02 mol per 100 gram fibers, the said treatment "being effectedafter carrying out the coagulation and before reducing the watercontents of the fibers in the drying to below 45% and the said univalentcation being selected from the group consisting of ammonium and alkalimetal ions.

5. The method of claim 4 wherein the alkali metal ions are selected fromthe group consisting of sodium and potassium ions.

6. The method of claim 4 wherein the Water soluble inorganic salts areselected from the group consisting of salts of sulfuric acid, phosphoricacid and nitric acid.

References (Zited in the file of this patent UNITED STATES PATENTS2,558,730 Cresswell July 3, 1951 2,904,391 Bennett et al Sept. 15, 19592,916,348 Cresswell Dec. 8, 1959

1. IN A WET SPINNING METHOD FOR PRODUCING FIBERS OF ACRYLONITRILEPOLYMERS SELECTED FROM THE GROUP CONSISTING OF POLYACRYLONITRILE ANDCOPOLYMERS OF AT LEAST 85% BY WEIGHT OF ACRYLONITRILE AND UP TO 15% BYWEIGHT OF MONOETHYLENICALLY UNSATURATED MONOMERS COPOLYMERIZABLETHEREWITH THE SAID METHOD INVOLVING DISSOLVING THE POLYMERS IN A NITRICACID SOLVENT, EXTRUDING AND SPINNING THE SOLUTION THUS OBTAINED IN ACOAGULATING BATH AND DRYING THE SPUN ARTICLE, THE IMPROVEMENT COMPRISINGTREATING THE FIBERS WITH A WATER SOLUBLE, UNIVALENT CATIONCONTAININGINORGANIC ACID SALT UNTIL THE UNIVALENT CATION IS INCORPORATED IN THEFIBER TO THE EXTENT OF BETWEEN 0.003 AND 0.02 AND MOL PER 100 GRAMFIBERS, THE SAID TREATMENT BEING EFFECTED AFTER CARRYING OUT THECOAGULATION AND BEFORE REDUCING THE WATER CONTENTS OF THE FIBERS IN THEDRYING TO BELOW 15% AND THE SAID UNIVALENT CATION BEING SELECTED FROMTHE GROUP CONSISTING OF AMMONIUM AND ALKALI METAL IONS.